Macromolecular structures determined by X-ray crystallography are central to modern understanding of biological processes and disease mechanisms and to the design of new medicines. Crystal damage caused by the X-rays themselves and by the cryoprotective procedures used to minimize radiation damage reduces structure resolution and accuracy -- of particular importance to mechanistic studies -- and in unfavorable cases can prevent structure determination. Powerful diffraction and real-space imaging techniques have recently been used to dissect disorder in macromolecular crystals, and provide new tools for understanding this damage. [unreadable] [unreadable] The long term goals of this project are to characterize the systematics of radiation and cryoprotection-induced disorder using simple model proteins and viruses; to develop new procedures for reducing this disorder so that the full potential of high brilliance synchrotron sources for data collection can be exploited; and to apply these to selected systems of significant biological interest. Radiation damage and damage caused by flash cooling are complex phenomena, and no single factor is likely to produce dramatic improvements. Systematic experiments using X-ray diffraction and imaging, atomic force microscopy and other techniques will evaluate the most important factors, and explore how they may be combined to optimize overall data quality. This approach has significant and realistic potential to impact how macromolecular structures are determined, and thereby to contribute to their use in medical, pharmaceutical, and agricultural applications.